In uplink of the radio communication system, when total transmission power of the communication terminal apparatus exceeds the maximum transmission powers it is necessary to stop transmission of one of channels or perform control such as decreasing a transmission rate so that the total transmission power does not exceed the maximum transmission power. In a Release99 specification of 3GPP (3rd Generation Partnership Project) of W-CDMA, as a method for realizing this, a transport format combination selection (hereinafter referred to as TFC selection) is standardized. Here, the maximum transmission power indicates smaller one of maximum allowable uplink transmission power set by a control station and maximum transmission power of the communication terminal apparatus.
In TFC selection, when data is multiplexed with a plurality of DCHs (dedicated channel) and transmitted, the communication terminal apparatus determines whether or not the total transmission power exceeds the maximum transmission power for each transport format combination (hereinafter referred to as TFC) that is a combination of transport format (hereinafter referred to as TF) indicating the amount of data or the like transmitted at each DCH, and selects a transmittable TFC. In the following explanation, a set of all TFCs is referred to as TFCS (transport format combination set).
TFC selection will be described in detail below using the drawings. FIG. 1 shows a case of having two DCHs of DCH#1 having three TFs and DCH#2 having two TFs (FIG. 1(A)). In this case, as shown in FIG. 1(B), six patterns of TFC1 to TFC6 exist. In addition, in FIGS. 1(A) and (B), the number of bits of each TF is indicated with the length of the horizontal axis.
Here, it is necessary to increase a transmission rate in accordance with an increase of the number of bits that have to be transmitted in a unit of time, and in order to obtain predetermined quality, it is necessary to increase transmission power in accordance with an increase of the transmission rate. In FIG. 1(C), transmission power of each TFC is indicated with the length of the horizontal axis, and a dotted line indicates maximum transmission power Pmax.
In the case of FIG. 1(C), the communication terminal apparatus determines that transmission is possible in TFC1 to TFC3 in TFCS since the total transmission power falls below maximum transmission power Pmax, and determines that transmission is impossible in TFC4 to TFC6 in TFCS since the total transmission power exceeds maximum transmission power Pmax and transmission power is insufficient. Then, the communication terminal apparatus selects one TFC from TFC1 to TFC3 where it is determined that transmission is possible.
Next, a detection function and TFCS restriction function in TFC selection of Release99 will be described using the drawings.
As shown in a state transition diagram of FIG. 2, the communication terminal apparatus detects elimination criterion/recovery criterion for each TFC for each one frame (15 slots) as a detection function. To be more specific, in the TFC in a supported state (the state where transmission is possible), when there are at least X slots (X does not have to be consecutive) out of preceding consecutive Y slots, where transmission power necessary for the TFC exceeds the maximum transmission power, the elimination criterion is detected, and the state transits to an excess power state (the state where power is excessive). Further, in the TFC in an excess power state or blocked state (the state where transmission is stopped) when there are preceding consecutive Z slots where transmission power necessary for the TFC does not exceed the maximum transmission power, the recovery criterion is detected, and the state transits to the supported state. In addition, parameters X, Y and Z use a value indicated in FIG. 3 as a default value.
FIG. 4 shows a timing of the TFCS restriction function. As shown in FIG. 4, in the conventional TFC selection method, the state transits to the supported state using a detection function, and after Tdelay—transition (with a default value of 60 ms), transits to the supported state using a restriction function. Further, the state transits to the excess power state using the detection function, and after Tdelay—transition, transits to the blocked state using the restriction function.
As described above, the communication terminal apparatus is capable of selecting optimal TFC for the current service out of a TFC group belonging to the updated supported state.
FIG. 5 shows an example of a timing of the detection function. In FIG. 5, the case where transmission power necessary for TFC exceeds the maximum transmission power is indicated as “×”, the case of not exceeding is indicated as “∘”. Furthermore, parameters X, Y and Z use a value indicated in FIG. 3 as a default value (X=15, Y=30, and Z=30).
At evaluation point 1, there are 10 slots in which the maximum transmission power is exceeded in a measurement period of immediately preceding consecutive 30 slots, and therefore the state does not transit from the current state. Furthermore, at evaluation point 2, there are 15 slots in which the maximum transmission power is exceeded in the measurement period, and therefore, when the current state is the supported state, the state transits to the excess power state.
Here, when a compressed mode occurs during transmission as shown in FIG. 6, a period where slots are not transmitted (transmission gap period) occurs. When the transmission gap period exists, it is not possible to apply the evaluation method using the above-described detection function, and a new evaluation method is required.    Non-Patent Document 1: 3GPP Release99 TS25.321 11.4